Various load testing apparatuses are known, including apparatuses for carrying out simultaneous compressive loading and shear loading of a test component that is to be load tested.
Generally, in such known apparatuses, the compression load may be introduced into the test component by means of a force introduction table and a pressure plate acting as a counter-support, between which the test component is received. For example, a force-regulated hydraulic cylinder acts on the force introduction table to move it toward the pressure plate, for example in a vertical direction, to thereby apply a regulated vertical compression load to the test component that is received between the force introduction table and the pressure plate. Furthermore, vertically oriented shear loads can be applied to the lateral vertical edges of the test component via two shear beams that are respectively secured to the two opposite vertical edges of the test component. One of these shear beams applies an upwardly directed force, while the other one of these shear beams applies a downwardly directed force, so as to apply the intended shear to the test component between its two opposite vertical edges.
More particularly, such a combined compression and shear load testing of a test component such as a curved aircraft component can be carried out using a particular conventionally known compression and shear testing apparatus, as follows. The main compression load is introduced vertically into the aircraft component through a force introduction table, which is moved by a force-regulated hydraulic cylinder, preferably in a vertical direction, toward a pressure plate that acts as a counter-support, with the aircraft component received between the force introduction table and the pressure plate. To introduce the compressive force into the aircraft component, the component is provided with special rim or edge reinforcements, so that the compressive force between the force introduction table and the pressure plate can be introduced into the body of the component without damaging its upper and lower edges.
Furthermore, the pressure plate is secured, e.g. bolted, to a head frame, which may be a stationary component of the machine frame. On the other hand, the compression loading hydraulic cylinder is supported on a base that is supported on a transverse girder which is supported from the machine frame by pivotally connected tension rods with integrated tensile force measuring transducers such as load cells. Additionally, a horizontal shear component can be introduced into the aircraft component by two hydraulic cylinders that are pivotally or articulately connected to the force introduction table.
Vertical shear forces including an upwardly directed shear component and a downwardly directed shear component are introduced into the opposite vertical edges of the aircraft component by two shear beams, respectively, having integrated force-regulated hydraulic cylinders. The effective direction of force application of the cylinders and thus of the shear beams is opposite one another, to apply the oppositely directed shear forces as mentioned above. The hydraulic cylinders are integrated into the shear beams, and particularly are installed pair-wise at a spacing or raster of e.g. 100 mm in the shear beams extending along the vertical edges of the aircraft component. For introducing the loads from the shear beams into the aircraft component, T-shaped load introduction brackets or fixtures are secured, e.g. screwed or bolted, to the aircraft component along the vertical edges thereof, similarly at a spacing or raster of 100 mm.
The force of the upwardly directed shear component is counter-supported or braced through two tension rods provided with tensile force measuring transducers or load cells that are pivotally connected to the first shear beam. The tension rods are further connected to the machine frame in a manner that is adjustable in a horizontal plane. On the other hand, the force of the downwardly directed shear component is counter-supported or braced through two compression struts or links that are provided with compressive force measuring transducers or load cells and that are pivotally connected to the second shear beam.
It is a disadvantage of the previously known conventional apparatuses that they can only be used for a hydraulic pressure up to about 350 bar, because a direct regulation is no longer possible for higher pressures in the hydraulic system. The regulation and the self-compensation of the forces is also in need of improvement.